Crosspoint switches are used to route signals from a plurality of inputs to a plurality of outputs. FIG. 1 illustrates an existing 4×4 crosspoint switch 100 that has four input ports 104A-104D and four output ports 108A-108D. The crosspoint switch 100 includes a switch array 112 for selectively providing signal paths between the input ports 104A-104D and the output ports 108A-108D. The switch array 112 includes four rows and four columns of switches 112. Each of input lines 116A-116D links the output of one of the input ports 104A-104D to a separate row of the switches 112. Each of output lines 120A-120D links a separate column of the switches 112 to an input of one of the output ports 108A-108D. Each switch 112 can selectively provide a signal path between one of the input lines 116A-116D and one of the output lines 120A-120D.
FIG. 2 illustrates an existing crosspoint switch 204 that routes signals from a plurality of source devices 208A-208N to a plurality of destination devices 212A-212N. The crosspoint switch 204 includes a switch array 216 for selectively providing signal paths between input ports 220A-220N and output ports 224A-224N. Each one of the source devices 208A-208N is connected to the switch array 216 via one of the input ports 220A-220N. Likewise, each one of the destination devices 212A-212N is connected to the switch array 216 via one of the output ports 224A-224N.
It will be appreciated that the source devices 208A-208N and the destination devices 212A-212N may not necessarily be connected to a same voltage source. For example, some of the source devices may be connected to a 1.8V source while the remaining source devices may be connected to a 3.3V source. Likewise, some of the destination devices may be connected to a 1.5V source while the other destination devices may be connected to a 2.5V source.
In existing crosspoint switches, the input ports receive power from a single voltage source. Referring again to FIG. 2, the input ports 220A-220N receive power from a voltage source Input_VDD. Because the input ports 220A-220N all receive power from a single voltage source, it is possible to match the input ports 220A-220N to only one of the different voltage sources connected to the source devices, but not all. Similarly, the output ports 224A-224N receive power from a single voltage source Output_VDD. Thus, it is possible to match the output ports 224A-224N to only one of the different voltage sources connected to the destination devices, but not all.
In order to connect the crosspoint switch 204 to a plurality of devices powered by different voltage sources, level shifters and buffers are generally used. Referring again to FIG. 2, the source device 208A is connected to a voltage source VDD 1. However, the input port 220A is connected to the voltage source Input_VDD. Since the source device 208A and the input port 220A are connected to different voltage sources, a level shifter 232A and a buffer 236A are connected in series to enable the source device 208A to connect to the crosspoint switch 216. Alternatively, an AC coupling capacitor may be used to facilitate such connections. For example, the source device 208B is linked to the crosspoint switch 216 via an AC coupling capacitor 232B and a buffer 236B.
Referring again to FIG. 2, the destination device 212A is linked to the switch 216 via a level shifter 240A and a buffer 244A that are connected in series. On the other hand, the destination device 212N is linked to the switch 216 via a coupling capacitor 240N and a buffer 244N. The use of level shifters and buffers increases the cost and complexity of a system. The use of AC coupling capacitors also increases complexity of a system and causes impedance discontinuities on a circuit board, resulting in signal degradation. The cost and complexities associated with utilizing AC coupling capacitors and level shifters can be avoided by DC coupling. However, in order to DC couple the input and output ports of the crosspoint switch to the source devices, the input and output ports of the crosspoint switch must be supplied from the same voltage source as the source devices.